docs: def mjpeg_url(self, channelno=None, typeno=None):
          """
          Return MJPEG streaming url
  
          Params:
              channelno: integer, the video channel index which starts from 1,
                         default 1 if not specified.
  
              typeno: the stream type, default 0 if not specified. It can be
                      the following value:
  
                      0-Main Stream
                      1-Extra Stream 1 (Sub Stream)
                      2-Extra Stream 2 (Sub Stream)
          """
          if channelno is None:
              channelno = 0
  
          if typeno is None:
              typeno = 1
  
          cmd = "mjpg/video.cgi?channel={0}&subtype={1}".format(
              channelno, typeno)
          return '{0}{1}'.format(self._base_url, cmd)